How do you check the weather?

[LennyJ1]

You can't just use any old stone, there is a master stone at the Met Office Headquarters, all others stones must match the porphyritic texture and contain the same number of phenocrysts with similar euhedral forms and as such the phenocryst count is inversely proportional to the accuracy of the stone. Many cheap Chinese copies are composed of a granodiorite and plagioclase composite which is fine when new but calibration drifts over a short period of time and can results in wild inaccuracies, e.g. it is rumoured that Michael Fish used one of these inferior stones on the morning the great October storm in 1987 

OMG LOL 

[ChuckMcB]

I suspect we have just tripped over a Met office in joke

Anyhow Metcheck gets my vote as well (when it's not down or throwing IIS 500 errors)...but only up to two/three days ahead, anything and everything else has at best a 50% chance of being true IMHO.